1. Field.
Disclosed herein are elements of superhard polycrystalline material synthesized in a high-temperature, high-pressure process and used for wear, cutting, drawing, and other applications. These elements have specifically placed superhard surfaces at locations where wear resistance may be required. In particular, disclosed herein are polycrystalline diamond and polycrystalline diamond-like (collectively called PCD) cutting elements with tailored wear and impact toughness resistance and methods of manufacturing them. One particular form of PCD cutting elements which may be used in drill bits for drilling subterranean formations are called polycrystalline diamond cutters (PDC's).
2. Description of the Related Art
U.S. Pat. No. 6,861,098 discloses methods for fabrication of PCD cutting elements, inserts, and tools. Polycrystalline diamond and polycrystalline diamond-like cutting elements are generally known, for the purposes of this specification, as PCD cutting elements. PCD cutting elements may be formed from carbon based materials with short inter-atomic distances between neighboring atoms. One type of polycrystalline diamond-like material known as carbonitride (CN) is described in U.S. Pat. No. 5,776,615. Another, form of PCD is described in more detail below. In general, PCD cutting elements are formed from a mix of materials processed under high-temperature and high-pressure (HTHP) into a polycrystalline matrix of inter-bonded superhard carbon based crystals. A trait of PCD cutting elements may be the use of catalyzing materials during their formation, the residue from which may impose a limit upon the maximum useful operating temperature of the PCD cutting element while in service.
One manufactured form of PCD cutting element is a two-layer or multi-layer PCD cutting element where a facing table of polycrystalline diamond is integrally bonded to a substrate of less hard material, such as cemented tungsten carbide. The PCD cutting element may be in the form of a circular or part-circular tablet, or may be formed into other shapes, suitable for applications such as hollow dies, heat sinks, friction bearings, valve surfaces, indenters, tool mandrels, etc. PCD cutting elements of this type may be used in applications where a hard and abrasive wear and erosion resistant material may be required. The substrate of the PCD cutting element may be brazed to a carrier, which may also be made of cemented tungsten carbide. This configuration may be used for PCD's used as cutting elements, for example, in fixed cutter or rolling cutter earth boring bits when received in a socket of the drill bit, or when fixed to a post in a machine tool for machining PCD cutting elements that are used for this purpose may be called polycrystalline diamond cutters (PDC's).
PCD cutting elements may be formed by sintering diamond powder with a suitable binder-catalyzing material with a substrate of less hard material in a high-pressure, high-temperature press. One method of forming this polycrystalline diamond is disclosed, for example, in U.S. Pat. No. 3,141,746, the entire contents of which are hereby incorporated by reference. In one process for manufacturing PCD cutting elements, diamond powder is applied to the surface of a preformed tungsten carbide substrate incorporating cobalt. The assembly may then be subjected to high temperatures and pressures in a press. During this process, cobalt migrates from the substrate into the diamond layer and acts as a binder-catalyzing material, causing the diamond particles to bond to one another with diamond-to-diamond bonding, and also causing the diamond layer to bond to the substrate.
The completed PCD cutting element may have at least one matrix of diamond crystals bonded to each other with many interstices containing a binder-catalyzing material metal as described above. The diamond crystals may form a first continuous matrix of diamond, and the interstices may form a second continuous matrix of interstices containing the binder-catalyzing material. In addition, there may be some areas where the diamond to diamond growth has encapsulated some of the binder-catalyzing material. These “islands” may not be part of the continuous interstitial matrix of binder-catalyzing material.
In one particular form, the diamond element may constitute 85% to 95% by volume of the PDC and the binder-catalyzing material the other 5% to 15%. Although cobalt may be used as the binder-catalyzing material, other group VIII elements, including cobalt, nickel, iron, and alloys thereof, may be employed.
U.S. Pat. No. 7,407,012 describes the fabrication of a highly impact resistant tool that has a sintered body of diamond or diamond-like particles in a metal matrix bonded to cemented metal carbide substrate at a non-planar interface. The catalyst for enabling diamond-to-diamond sintering may be provided by the substrate. The general manufacture of a PDC, insert, or cutting tool may use a cemented carbide substrate to provide a catalyst to aid in the sintering of the diamond particles.
Published US Patent Application US 2005/0044800, describes the use of a meltable sealant barrier to cleanse the PCD cutting element constituent assembly via vacuum thermal reduction followed by melting the sealant to provide a hermetic seal in a can used for the further high temperature, high pressure (HTHP) processing—with a temperature which may be higher than 1300C and a pressure which may be greater than 65 KBar. The sealing of the can may be required to limit contamination of the diamond particle bed during HTHP processing, and to also maintain a high vacuum in the can to limit oxidation and other contamination. The HTHP can assemblies may help to prevent contamination of the PCD cutting element table and may also be sealed by using processes, such as EB welding, used for standard production of cutters and inserts.
U.S. Pat. No. 6,045,440 describes a structured PDC that is oriented for use in earth boring where formation chips and debris are funneled away from the cutting edge via the use of raised top surfaces on the PDC. The redirection of the debris may be achieved by creation of high and low surfaces on the PDC cutting surface. A method used to form the protrusion on the PDC is not described in detail in this patent, the surface texture and geometry of this cutter surface may be limited to the ability to extrude and/or form sealing can surfaces that are a negative of the desired PDC front face extrusions, or alternatively formed by post HTHP processing, such as EDM and Laser cutting—as may be necessary to form the surfaces on the cutter face.